A special problem associated with laundry cleaning is the removal of stains of a fatty nature. Currently, fat-containing dirt is emulsified and removed using a combination of elevated temperature and high alkalinity. However, there is a recent strong tendency toward the use of relatively low washing temperatures, namely about 40.degree. C. or lower, conditions particularly unsuited for fatty stain removal. There is therefore a need for detergent additives which are effective at the lower washing temperatures, stable in high alkaline detergent solutions and stable under storing conditions in both solid and liquid detergent compositions. A group of enzymes which hydrolize triglycerides are lipases (E.C. 3.1.1.3). Lipases are widely distributed, occurring in many different prokaryotic organisms, as well as eukaryotic cells. Depending upon the source of the enzyme, substrate specificity as well as other characteristics including stability under various conditions, varies widely. Lipases have been used in detergent compositions, however those used exhibited low cleaning efficiency under washing conditions and in addition, did not meet the stability requirements for detergent use.
Lipolytic enzymes which are capable of exhibiting lipase activity under modern washing conditions, i.e., they are stable and effective at high detergent concentrations, at high pH and at low washing temperatures, are produced by certain strains belonging to the species of Pseudomonas pseudoalcaligenes, Pseudomonas stutzeri and Acinetobacter calcoaceticus (see European Patent Application EP-A-0218272). However, these species are potentially pathogenic for plants and animals, and few data are available on the fermentation conditions required for an effective production process for lipases using these microorganisms.
It is therefore desirable to develop an efficient and safe way to produce lipolytic enzymes having the desired characteristics for detergent additives. Moreover, it is desirable that the lipases be secreted by the host organism so that the enzyme may be recovered directly from the extracellular fluid of the fermentation mixture.